In many fields of microelectronics, a matrix is composed of storage, sensor, actuator or image elements. The individual elements must be actuated with an address, without disturbing neighboring cells. For storage components, such matrix arrangements play an important role in achieving high storage densities and rapid access speeds and obtaining a replacement for the typical flash storage of today.
One generally distinguishes between a passive and an active matrix (e.g., Willem den Boer: “Active Matrix Liquid Crystal Displays. Fundamentals and Applications” 1st Edition, Elsevier, 2005 and Temkar N. Ruckmongathan: “Addressing Techniques of Liquid Crystal Displays”, Wiley, 2014).
The passive matrix consists of mutually perpendicular metal lines, which subtend the rows (bit lines (3)) and columns (word lines (2)). At the crossing points, cells (4) are defined, in which the active medium (1) can be actuated by a current flow (11) or an electric field. The benefit of this arrangement is that it is easy to produce and very high densities (4F2 with F being the minimum featured size) can be achieved for storage chips. The major drawback hindering the application of a passive matrix thus far is the fact that the neighboring cells undergo parasitic interference. Only in organic ferroelectric storages can this principle be used, but this has drawbacks in terms of material wear and storage time (EP 1 316 090 B1; EP 1 798 732 A1; US 2006/0046344 A1; US 2002/0017667 A1; US 2003/0137865 A1).
The active matrix uses an active electronic element for the actuation of the individual elements. This can be a diode or a transistor. The diode would offer the advantage of a compact design and exactly the same high density for storage chips as in a passive actuation (4F2). However, a diode in resistive elements often has the problem that the ON/OFF ratio is too low and in liquid crystal displays poor contrast is achieved. Furthermore, a diode itself acts as a capacitance and if the elements being actuated are themselves capacitances, as in the case of liquid crystal displays (US 2011/0090443 A1)/electronic paper (US 2008/0043317 A1)/micro mirror arrays (U.S. Pat. No. 5,583,688) or ferroelectric storages (EP 1 316 090 B1), an actuation is difficult (voltage divider). Diodes may often be used for resistive storage elements (US 2006/0002168 A1; WO 2003/85675 A2).
A transistor actuation (US 2003/0053351 A1; U.S. Pat. No. 6,438,019) enables significantly higher ON/OFF ratios and furthermore capacitances can be switched. Furthermore, the contrast is easy to control for monitor screens. The drawbacks are more manufacturing steps and usually a rather high space requirement for storage devices.
In general, one distinguishes in the case of storages with transistor actuation between the NAND (U.S. Pat. No. 5,088,060) and the NOR architecture (U.S. Pat. No. 7,616,497), wherein the NAND architecture makes possible high storage densities (4F2), but requires significantly longer access times. The NOR architecture has a higher space requirement (6-8F2), but on the other hand is fast (Betty Prince: “Semiconductor Memories: A Handbook of Design, Manufacture and Application”, 2nd Edition, Wiley, 1995). The drawbacks of these two different architectures, along with corresponding storage materials, form one of the reasons why thus far there is no universal storage that replaces SRAM, DRAM, flash storage and hard computer disk. Therefore, an architecture which combines the benefits of the NAND and NOR architecture would be desirable. A universal storage would have to meet several specifications, among which are a high storage density, a high read and write speed, as well as a sufficiently large number of read/write cycles. Another criterion in terms of mobile applications is a low energy consumption. One possible alternative technology to the flash storages is ferroelectric storage, which possesses at present a high number of read/write cycles (1012-1015) and is roughly as fast as DRAM storage. The biggest problem thus far is the scalability and the storage density, since ferroelectric materials are little compatible with silicon-based CMOS logic.
New storage technologies are also important in terms of artificial neural nets. In traditional computers, the processing and storage of information are strictly separate, whereas the brain does not possess such a separation, and for this reason a nonvolatile storage solution must be created, one which can be easily embedded in the processing units. An artificial neural net consists of neurons and synapses, which store weights for example in the form of a resistance value. The neurons usually have a sigmoidal transient response for the activation function, so that a rather complicated transistor circuit is often necessary (U.S. Pat. Nos. 3,476,954; 8,694,452), having a high energy consumption and being difficult to produce. Likewise, so-called Rectified Linear Units (ReLU) are used as activation functions for artificial neurons.
In patent DE 10 2010 045 363 B4 there has already been published a semiconductor sensor which can modulate a static field into an alternating field. The patent deals with a modulation of the mobile charge carrier concentration in a semiconductor to control an electric field or potential. For this, the so-called Debye-length is utilized, which gives the typical shielding length of a field in a solid as
            L      D        =                                        ɛ            0                    ⁢                      ɛ            r                    ⁢                      k            B                    ⁢          T                                      e            2                    ⁢          2          ⁢          n                      ,whereLD: is the Debye-lengthε0: is the electric field constantεr: is the relative dielectric constant of the materialkB: is the Boltzmann constantT: is the temperaturee: is the elementary chargen: is the mobile charge carrier concentration (electron and hole concentration).The field describes for low fields an exponential decrease in the solids by
      E    =                  E        0            ·              e                  -                      x                          L              D                                            ,whereE: is the electric field strength in the solidE0: is the field strength at the beginning of the solid with x=0x: is the position in the solid.
If the mobile charge carrier concentration n is very low, the Debye-length is slight and the field can easily pass through the solid, provided the latter is significantly thinner than the Debye-length. But if the mobile charge carrier concentration is high, the field will be well shielded, and if the mobile charge carrier concentration is modulated, the transmitted field will be transmitted with different strength and be converted into an alternating field. In this way, a switch is realized for electric fields.
The problem which this invention proposes to solve is therefore to make possible an active actuation of capacitive elements in a matrix with the benefits of a passive actuation (simple manufacture, high storage density, fast access time). At the same time, it should be possible to model more easily the activation function of a neuron in regard to artificial neural nets.